Plasma heating systems



Oct. 4, 1965 REBOUX PLASMA HEATING SYSTEMS Filed Jan. 20, 1964 United States Patent tion of France Filed Jan. 20, 1964, Ser. No. 338,933 Claims priority, application france, Jan. 22, 1963,

Claims. 611219-1049 The present invention relates to heating systems using ionized gas or plasma as heating medium. More particularly the invention relates to plasma furnaces or torches in which the temperature obtained by induction heating is raised by causing a D.C. or A.C. current to flow through the ionized gas.

According to the invention there is provided an ionized gas heating ssytem, which may be for example in the shape of a furnace or of a torch or blow pipe, comprising a chamber into which the gas to be ionized is discharged, the chamber supporting a primary winding, and including a secondary winding, comprising one turn shaped as metal cylinder, having a gap along at least one generatrix thereof and showing, at the outlet port-ion of the chamber, a hollow shell, this shell being also divided in at least two sectors by said gap, said sectors being insulated from each other and respectively connected to the terminals of a D.C. or A.C. supply.

The invention will be best understood from the following description and the appended drawing wherein;

FIG. 1 shows an axial section of a heating system according to the invention;

FIG. 2 shows the current flow in the secondary turn of a system according to the invention; and

FIGS. 3 and 4 show modifications of the arrangement shown in FIG. 2.

FIG. 1 shows an axial section of the supply head of ionized gas induction heating apparatus according to the invention.

A primary winding 1 surrounds a cylindrical conductor 2, which forms the only secondary winding turn and whose lower part, situated at the outlet of the discharge cham ber 10, forms a double walled cylinder or shell 20 and can be cooled by means of any suitable medium 23, for example liquid, flowing therethrough.

According to the invention, shell 20 is partitioned into two sectors by diametral splits or gaps, as shown in FIG. 2, or in a plurality of sectors, as shown in FIGS. 3 and 4.

The walls of each gap are preferably coated with a thin isolating material of, say, mica.

Each of the sectors thus built up forms one secondary turn for the primary winding 1.

The wall of cylinder 20 supports a sheath 4, which is heat-proof and is, for example, of quartz, and guides the plasma generating fluid, which is fed into chamber through a duct 6 formed in upper cylindrical plate 5.

An electrode 51, made of tungsten, extends, in the embodiment shown in FIG. 1, through the center of plate 5. This electrode is used for priming the ionization in conjunction with another movable electrode (not shown) which is inserted into chamber 10 through the outlet 71 of chamber 10.

Electrode 51, may be fitted with a central bore so that 3,277,265 Patented Get. 4, 1966 "ice it may be possible to inject any suitable powdered material within the plasma, for electro-thermal treatment purposes.

In the embodiment of FIG. 2, cylinder 20 has been divided in two sections 21 and 22, separated by two diametral gaps. The current flows in the outer walls is in the direction of arrows 21a and 22a, and in the inner walls in the direction of the arrows 21b, 22b.

It is to be noted that the length of the path along which the current flows is greater with two gaps than would be the case with one gap.

The two half shells 21 and 22 are insulated from each other by the gaps, and by connecting them, at terminals 31 and 32 respectively, to the terminals of a D.C. or A.C. supply source 3, a current can be made to flow through the ionized gas.

Inductance coils 33 and 34, placed in series with the supply, and capacitors 35 and 36, connected as shown, protect source 3, and filter noise frequencies delivered by generator 3, to avoid any interference thereof within the plasma.

FIGURES 3 and 4 are modifications of the portion 20 of the structure.

In the embodiment shown in FIG. 3, there are four shell portions insulated from each other; A.C. or D.C. potential difference can then be created between them.

In the embodiment of FIG. 4 there are only two half shells, but each of them has a plurality of radial recesses which contribute to increase the paths followed by the surfaces current flow.

The partition of shell 20 extends over all the height of cylinder 2.

Of course the invention is not limited to the embodimenst described and shown which were given solely by way of example.

What is claimed is:

1. An induction heating system comprising: a chamber having an inlet for ionizable gas and an outlet for ionized gas; a conductive wall surrounding said chamber; a primary winding surrounding said wall; said wall serving as a secondary coil for said primary winding; said wall having a hollow portion bounding said outlet and comprising at least two sections, insulated from each other along the direction from said inlet to said outlet; and means for providing an additional potential difierence between said sections.

2. An induction heating system comprising: a chamber having an inlet for ionizable gas and an outlet for ionized gas; a conductive wall surrounding said chamber; a primary winding surrounding said wall; said wall serving as a secondary coil for said primary winding; said wall having a hollow portion bounding said outlet and comprising a plurality of sections insulated from each other along the direction from said inlet to said outlet; and means for providing an additional potential difference between said sections.

3. An induction heating system comprising: a chamber having an inlet for ionizable gas and an outlet for ionized gas; a conductive wall surrounding said chamber; a primary winding surrounding said Wall; said wall serving as a secondary coil for said primary winding; said wall having a hollow portion bounding said outlet and comprising at least two sections insulated from each other along the direction from said inlet to said outlet; supply means for providing an additional potential difference between said sections; means for connecting said supply means to said sections, said means comprising filtering means for filtering the higher trequencies.

4. An induction heating system comprising: a chamber having an inlet for ionizable gas and an outlet for ionized gas; a conductive wall surrounding said chamber; a primary winding surrounding said wall; said wall serving as a secondary coil for said primary winding; said wall having a hollow portion bounding said outlet and comprising at least two sections insulated from each other along the direction from said inlet to said outlet; said hollow portion comprising a plurality of recesses and means for providing an additional potential difierence between said sections.

5. An induction heating system comprising: a chamber having an inlet for ionizable gas and an outlet for ionized gas; a conductive wall surrounding said chamber; a primary winding surrounding said wall; said Wall serving as References Cited by the Examiner UNITED STATES PATENTS 1,997,741 4/1935 Northrup 2l9l0.49 2,537,289 1/1951 Van Embden 2l9l0.49 2,644,881 7/1953 Schorg 219-1051 3,129,351 4/1964 Martinek 219-75 RICHARD M. WOOD, Primary Examiner.

L. H. BENDER, Assistant Examiner. 

1. AN INDUCTION HEATING SYSTEM COMPRISING: A CHAMBER HAVING AN INLET FOR IONIZABLE GAS AN OUTLETFOR IONIZED GAS; A CONDUCTIVE WALL SURROUNDING SAID CHAMBER; A PRIMARY WINDING SURROUNDING SAID WALL; SAID WALL SERVING AS A SECONDARY COIL FOR SAID PRIMARY WINDING; SAID WALL HAVING A HOLLOW PORTION BOUNDING SAID OUTLET AND COMPRISING AT LEAST TWO SECTIONS, INSULATED FROM EACH OTHER ALONG THE DIRECTION FROM SAID INLET TO SAID OUTLET; AND MEANS FOR PROVIDING AND ADDITIONAL POTENTIAL DIFFERENCE BETWEEN SAID SECTIONS. 